The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.
Recently, a mobile communication system providing a communication service through a plurality of frequency bands is operated. For example, an LTE system may also manage two or more frequency bands, and use a method of distributing loads according to the number of users to which one BS can provide services. In this case, a cell reselection or redirection function in which the UE naturally moves between frequency bands through a parameter configuration according to a priority of the UE may be used.
However, the inventor(s) has noted that, an operation in which, when an access attempt by the UE fails due to the occurrence of temporary overloads or errors in a cell of a particular LTE frequency band, the UE performs the access attempt in another frequency band, is not defined. For example, with respect to a UE operation when there is no response to Random Access Channel (RACH) preamble, the 3GPP TS36.321 standard discloses only a re-access attempt in one cell without consideration of another LTE frequency band.
Accordingly, the inventor(s) has noted that, in order to efficiently operate a mobile communication system using a plurality of frequency bands, a method of intelligent access of the UE in various frequency bands is required.